In accordance with the advance of wireless communication systems, services provided by the wireless communication systems are various. Further, to stably provide the various services of good quality, a rapid wireless data transmission technique is required. Various systems and methods have been suggested to realize the rapid wireless data transmission. Research is still conducted regarding faster data transmission techniques at the lower cost. The rapidly growing wireless communication systems need a separate frequency band for the coexistence with the existing techniques. However, frequency resources are limited and the existing systems are occupying most of the frequency resources.
In the frequency resource occupied by a particular system, the corresponding frequency band is not always in use. Accordingly, a scheme under consideration detects a time interval of the unused frequency resource and utilizes the frequency resource in the detected time interval. A wireless communication system based on Cognitive Radio (CR) is devised to carry out the wireless communication by reusing the temporarily free frequency resource occupied by the particular system. For example, a Television (TV) band frequently includes the frequency resource temporarily out of use. The Institute of Electrical and Electronics Engineers (IEEE) 802.22 is developing a standard for technical conditions required for the radio communication and solutions to the related problems, without affecting the TV broadcasting system.
In the CR based wireless communication system, the available band is determined depending on whether a licensed system uses the frequency resource or not. Hence, a base station of the CR based wireless communication system divides the frequency resources in the same unit as the frequency band unit used by the licensed system. For example, in the TV broadcasting system, the unit of the used frequency resource is a channel. The base station of the CR based wireless communication system needs to transmit control information per channel for terminals connected to the channels. The control information transmitted per channel passes through modulation and coding schemes according to a channel quality to make sure of the reception, and a repetitive coding. In other words, considerable overhead caused by the control information is inevitable. Thus, what is demanded is a method for reducing the overhead caused by the control information in the CR based wireless communication system.